Abstract: Between an exhaust chamber and a lubrication chamber, a second seal that seals between a cylinder that partitions the exhaust chamber and a first shaft and a first seal that seals between a side cover that partitions the lubrication chamber and the first shaft are provided. A gas introduction space to which a seal gas is supplied is provided between the second seal 2 and the first seal. The second seal and the first seal each have a base part and a pair of ring-like lips extending from the base part toward the first shaft. The pair of lips extends such that the distance therebetween is gradually increased from the base part toward the first shaft, and the tips of the pair of lips can be brought into elastic contact with the first shaft.